Moving picture sound recording and reproducing apparatus



-WFE Feb. 25, 1936. P. SAFRANSKI El A1. 3 1 9 MOVING PICTURE SOUND RECORDING AND REPRODUCING APPARATUS Filed-Jun 29, 1955 ELEVATION AHPU HEP 2 5/ PLAN t PLAN l NVENTO R5 ATTORNEY Patented Feb. 25, 1936 I UNITED STATES PATENT OFFICE MOVING PICTURE SOUND RECORDING AND REPRODUCING APPARATUS 1 Claim.

The purpose of this invention is to improve the recording and reproduction of sound upon and from motion picture films and perfect the same to such an extent that sound may be efiiciently 5 recorded and reproduced upon and from 16 mm. or other small film, and also film traveling at a comparatively slow" speed.

The invention, therefore, relates to the recording and reproduction of sound thru a sound track upon motion picture film, or the recording or photographing of amplified electrical sound impulses upon a photographic film and the reproduction of thesephotographed impulses therefrom.

The invention is in the use of a crown or other glass element having directly opposed concave cylindrical surfaces in the opposite sides thereof independent of, or in combination with, a bi-convex or other lens and a light gate consisting of a narrow slit aligned with the axis of the concave surfaces, and these members are in combination with an achromatic objective lens system having a diaphragm with a small aperture on the optical axis functioning as a trimmer for the light beam projected thru the objective lens system.

Other methods for recording and reproducing sound on and from narrow gage film have been used, however, these have not been refined to such an extent that they operate satisfactorily at the slow speeds required by small film. The

method of using a slit with a beam of light focused upon it and projecting the image upon the film is well known but its limitations are reached and its difficulties are increased when the aperture is reduced below .001 inch.

36 It is also possible to record and reproduce sound using a ribbon filament and an optical system of lenses to reduce the image of the filament, however, in this system any mechanical defect in the ribbon filament is photographed in recording, and

40 when used for reproduction, it is impossible to obtain pure tones and produce a maximum response if the ribbon filament is even slightly warped. Its limits are also reached as the light beam on the film reaches a size of about .001 inch.

45 It is also possible to use a glass body having a single concave cylindrical surface ground upon one side only thereof, and with various convex curves or cylinders ground on the opposite side, such as a convex cylinder, a convex spherical sur- 50 face, or a plane surface, and this will produce a narrow beam, but this beam loses its brilliance as the concave cylindrical curve is made smaller in order to produce a light beam less than .0005 inches.

55 The object of the invention is, therefore, to

provide a method of recording and reproduction of sound upon and from the sound track of motion picture film by which sufficient light may be projected to produce a light beam sufliciently thin to record and reproduce with narrow gage 5 and slow speed film.

Another object of this invention is to provide a method of reproduction of the sound track of motion picture film which method is thoroughly dependable. 10

Another object is to provide a method of reproduction of the sound track of motion picture film, in which the efliciency is increased over previously known methods.

Another object is to provide a method of sound 15 recording and sound reproduction of motion picture film in which the high limit of frequencies is increased.

Another object is to provide a method of recording and reproducing sound film which pro- 20 vides a means of obtaining, with a minimum cost of maintenance, and the elimination of highly skilled operators, the maximum efiiciency from a photographic sound track on film.

Another object of the invention is to provide a 25 method of recording and reproducing sound thru film in which the critical adjustments necessary in heretofore known. methods are dispensed with, making it ideal for use in schools, homes and automatic advertising, or other devices, where 30 high quality sound is desired with a minimum of professional skill.

Another object is to provide an. optical method of producing a fine beam of light which can be made as narrow as .0002 inches and less.

Another object of this invention is to provide a means of recording and reproducing frequencies up to and above ninety-five hundred cycles at a film speed of 18 inches per second.

Another object of this invention is to provide an optical method and system for the reproduction of sound which system produces a fine thin light beam and retains its brilliance at a high enough level to produce at the photo-electric cell a higher output in micro-amperes than heretofore known in existing systems.

Another object of this invention is to provide a. system and apparatus which can be manufactured at a low cost and which can be installed, adjusted, and maintained at a minimum cost.

Another object of this invention is to provide a system and apparatus which will respond to frequencies over a wide audio range, below cycles per second to above 9500 cycles per second, which feature makes possible the recording and repro- 55 duction of the sound track with all of the fundamental tones, and accompanying characteristic harmonics, of all orchestral instruments and voices within the above frequency range and which thereby provides naturalness of tone to the reproduction of sound and eliminates the difficulty formerly encountered by existing known systems of reaching the high frequencies.

Another object of this invention isto provide a method and sound reproducing apparatus which has sufiicient volume to fill a large theatre or music hall or the like, where the output level at the photo-electric cell must be high.

Another object of this invention is to provide an optical system which will respond uniformly giving what is known as a fiat curve to all of the frequencies between the limits from below 55 cycles per second to above 9500 cycles per second.

A particular object of this invention is to provide a method and apparatus which will successfully record and reproduce the sound track upon the narrower gage film, such as that of 16 mm. width.

A further object is to provideasystem which will overcome the formerdifiiculty of recording and reproducing the higher frequencies upon a 16 mm. film, which' film necessarily travels at a slower surface speed, requiring a smaller beam or aperture to attain the above result.

A still further object is to provide a. system and apparatus which will successfully reproduce sound from-1'6 mm. film, as in a home projector, which system inits simplicity permits ease of operation and adjustment such asfocusing the beam on the sound track, positioning the exciter lamp.

And a still further object isto provide an optical system and apparatus which will reproduce frequencies as high asninety-five hundred' cycles at the slower surface speed required by the 16 mm. film;

With these ends in view the invention embodies a glass element of crown glass, or other glass, having two opposed parallel concave cylindrical surfaces in its opposing faces, which element is mounted in a. casing independent of or in combination' with a lens and having a light gate in the form of 'aslit also parallel with the axis of said cylindrical surfaces and these members are combined with an achromatic objective lens system having. a trimmer diaphragm in combination therewith. All of these elements are mounted in aca'sing and positioned between a lamp or" other source-of" light and a film having a sound track thereon and with a photo-electric cell on the opposite side of the film: All of the above elements including the sourceof light andphoto-electric cell are positioned on the optical axis extending thru the parallel'concave' cylindrical surfaces and objective lens system.

Other features and advantages of the invention will appear from the following description taken in connection with the drawing, wherein:

Figure I is a diagrammatic view showing the general arrangement of the invention with the parts positioned on an optical axis extending from asource of light thru the lens system and thru the film to the photo-electric cell.

Figure 2 is a View showing a front elevation of an element for producing the light beam and a casing in which the light gate is f0-rmed, in which the element is mounted.

Figure 3 is a longitudinal section thru the easing in which the lens system maybe contained.

Figure 4 is an end view showing the achromatic objective lens system with the aperture forming the trimmer opening in the diaphragm shown in dotted lines.

Figure 5 is a side elevation showing the element with the opposed concave cylindrical surfaces in the sides thereof.

Figure 6 is a front view of the element shown in Figure 5.

Figure 7 is a.- view showing an element of an alternate design in which the unnecessary portions of the element beyond the edges of the concave portions are omitted.

Figure 8 is a view showing an element of an alternate design in which the double concave portions are positioned inside of the element and formed by grinding a cylindrical opening therethru.

Figure 9 is a view showing an element of an other alternate design in which one end thereof is beveled providing a deflecting surface for reflecting the ray as in a prism.

Figure 10 is a diagrammatic view showl'ng'a;

plan view for a combination element with the concave surfaces formed by an opening therethru and convex surfaces of the lens shown' Figure 1 ground on the opposite ends thereof.

Figure 11 is another diagrammatic view showing a plan view of an element having a prismatic surface with the double concave cylindrical surfaces extending therethru and a convex cylindrical surface formed" at one end.

Figure 12 is another diagrammatic View showing a prismatic element in elevation but with its double internal concave cylindrical surfacerotated to that in Figure 11- and having 2.

spherical instead of cylindrical curve at thefront'. Figure 13' is a view showing a detail of the achromatic objective lens system.-

Figure 14 is aview showing the first crown glass lens of the objective lens system;

Figure*15 is'a view showing: the flint lens of the objectivesystem.

Figure 16 is a diagrammatic view showing an arrangement of the lens system asit may be used" for recording.

The optical axis is indicated by the letters A-B throughout the drawing.

In the drawing the apparatus is shown as it would be made'wherein' numeral l indicates a; lamp or any source of light, numeral 2 a photo electric cell, and numeral 3 a' casing in which the lens system is mounted;

The invention particularly relates toain element having opposed double concave parallel cylindrical surfaces 5* and 6 extending thereacross, as shown inFi'gures-E, 6; and '7. The'sesurfaces may be of any desired radius or may be formed with several radii, and maybe cylindrical, parabolic; or of any concave curvature. It is preferred to grind these surfaces in the opposite sides of an element, as shown in Figure 5' or 7 however,

they may also be ground thru an element 1, as

the angle of this bevel maybe45 so that the" optical axis willbe reflected at an angle of 90 or the surface may be formed at any angle in' order toreflect the optical axis to any point or points desired. This surface may also be par-- allel to the axis of theconcave surfaces, as

One of these surfaces may alsobeshown in Figures 9 and 12, or at an angle to the axis of these surfaces, as shown in Figure 11.

The element 4 may be made in the form of a disc, as shown in Figures 1, 5 and 6, or the portions 9 and I8 beyond the edges of the concave surfaces may be omitted providing fiat sides II and H, as shown in Figure 7 in which the element is indicated by the numeral 13. These surfaces may, however, be of any shape or design and the ends may be curved, as shown in Figure 2. so that they will correspond with the curvature of a cylindrical casing in which the element may be placed, or shaped to correspond with any device with which it may be used. In the design shown in Figures 2 and 3 the element 13 is mounted in slots [4 and IS in the sides of a housing l6, and a light gate I1 is formed by a slot extending across a disc I8 at the end of the housing l6 and this slot is parallel to the axis of the concave surfaces of the element I3. It will be understood that the light gate may be of any width and may be formed in any manner and also may be positioned any distance desired from the element l3. The light gate may also be formed and mounted independent of the element and any means may be used for holding the light gate in relation thereto. The distance from the light gate to the element may also be varied and this distance may be adjusted for different conditions. Means may also be provided for adjustably mounting the light gate in relation to the element so that the distance between the gate and element may readily be adjusted, as desired.

This light gate is of a substantial width which may be from 'l/64 to 2 of an inch depending upon the curvature of the concave cylindrical surfaces 5 and 6 and is, therefore, not to be confused with the narrow slit of an existing system which cannot successfully operate if the slit is larger than .002 of an inch. This light gate is for the purpose of eliminating stray light and rendering a dark field above and below the light beam and when used in combination with the double .concave cylindrical surfaces of the element 4,

tends to concentrate, by eliminating the stray light rays, 9, maximum amount of bright rays to produce a very thin light beam of maximum intensity, whereas the slit normally used in an existing system cuts off or eliminates all light rays except those passing directly thru the very fine slit. The light gate of this invention is, therefore, not merely a thin slit thru which light rays may pass but is an opening of substantial thickness thru which refined rays may pass from a special element which, in itself, collects the light rays which are preferable for use in the light beam and diverges all other light rays. This gate is, therefore, not an essential element and may be dispensed with as its only purpose is to eliminate these diverged rays, thus creating a dark field above and below the luminous line. This system will operate successfully without the light gate.

In the design shown in Figure 3 a lens [9 is positioned at the end of the housing IS with a plane surface 20 at one side of the element and a convex surface 2| at the opposite side. This lens may be double convex, .as shown in Figure 1 in which it is indicated by the numeral 22, cylindrical, spherical, toric, or any shape. It may also be positioned adjacent the element I3 as shown in Figure 3 or spaced apart therefrom by a spacer 23, as shown in Figure 1, and the spacer may be of any length or size in order to hold the lens any distance desired from the element which in the design shown in Figure 1 is indicated by the numeral 4. The light gate I1 is also shown as a separate and independent element in Figure 1 and it will be understood that this may be independent of the element 4 and positioned at any distance therefrom, as may be desired. The housing 16 may be placed in the end of the casing 3 and held against a shoulder 24 by a threaded ring or collar 25 which is threaded in the end of the casing, as shown. This cylinder may, however, be held by any other means and the element, light gate, and lens may be mounted in the casing in any other manner or in any other position.

This cylinder with the element having the concave surfaces and light gate may be positioned so that the axes of these concave surfaces of the element are perpendicular or at right angles to the direction of motion of the film thereby producing a light beam extending transversely of the film.

The achromatic objective lens system is preferably positioned in a member 26 which is threaded in the opposite end of the casing 3 and a threaded sleeve 21 is threaded into the center of the member 26 from the inner end thereof which will hold the first lens 28 and in the end of which is a diaphragm 29 having an aperture 38 in the center thereof which functions as a trimmer to trim the outer rays of the light beam and thereby define the light beam sothat the actual size of the light beam passing thru this diaphragm may be defined and pre-determined. The aperture 30 may be of any size or shape and the diaphragm 29 is preferably thin or may be of any thickness. This trimmer opening may also be provided in the casing in any other manner or by any other means and the distance thereof from the objective lenses 28 and 3| may be varied or adjusted as may be desired. The first objective lens 28 rests on a shoulder in the opening in the inner end of member 25 and is shown held in place by the threaded sleeve 21, and the second objective lens 3| is mounted in the outer end of the member 26 in an opening 32 and the outer edges of the opening may be peened over to hold the lens of the lens may be held in any manner or by any means.

This objective lens system is shown in detail in Figure 13 in which the lens 28, which is flint, is provided with a crown glass member 33, and the lens 3| is also of crown glass, thereby providing a crown glass member 33 thru which the light beam first passes, a flint lens, and then another crown glass lens. The index of refraction of the first crown glass member 33 is preferably 1.50 and that of the second crown glass member 3! is 1.52. It is also preferred to make the diameter of the members 28 and 33 of an inch and that of the member 3| 4 of an inch. The radius of the outer surface 34 of the lens 33 is 8.75 mm., that of the inner surface 35 and also of the concave surface of the flint lens 28 8.75 mm. and the radius of the outer surface of the lens 3| is 8.5 mm. The rear surfaces 31 and 38 of the lenses 23 and 3| are plane. It will be understood that although it is preferred to use lenses of the dimensions given, these dimensions may be varied and lenses of any other refraction or radii may be used. It will also be understood that any other achromatic objective lens system may be used instead of this-system or may be used in combination or independent thereof, as may be desired.

From the achromatic lens system the light beam continues to travel on the optical axis thru the film which is indicated by the numeral 39 and from the film to the photo-electric cell 2. The film is positioned so that the optical axis will pass thru the sound track thereon and, in the diagram shown in Figures 1, l2, and 16, parts are shown in elevation so that the film will travel upward or downward, whereas in Figures 10 and 11, the parts are shown in plan so that the film is shown in cross section and the sound track is indicated by the numeral 40. It will be understood that the sound track may be of any size or positioned at any point or points and the frequencies or impulses photographed thereon may be of any type.

The achromatic lens system converges the available light to the focal point and forms, in the secondary plane, a long thin beam of light which is the light of the filament viewed thru the double concave cylinder. This thin light beam intercepts the film at the sound track and thence diverges until the light strikes the photo-electric cell 2. The shape of the image upon the photo electric cell is determined by the shape of the trimmer aperture 30 in the diaphragm which is positioned in the primary focal plane of the obj ective lens system. The size of the image upon the photo-electric cell is determined jointly by the focal lengths of the various elements in the casing, the collective lens 22, the element 4, the objective lens system, the distance of the lens 22 from the light source I, and the distance of the objective or achromatic lens system from the photo-electric cell 2. The size of the image at the photo-electric cell is also directly dependent upon the size of the aperture 30 in the diaphragm 21. The photo-electric cell may be placed in any electrical circuit in any well known and standard systems in which there is a potential between the leads or connections thereto thru a resistance. The variations of light at the photo-electric cell due. to the variations of density or area upon the sound track of the film cause a corresponding change in the potential applied to the electrodes of the cell and it is this change in potential which is amplified with an amplifier pref erably of the vacuum tube type. After sufficient amplification the signal is placed upon the coil of a loud speaking telephone, or a dynamic speaker, or magnetic or crystal speaker, to be converted into audible sound.

The description and dimensions hereinbefore specified are of a model which operates successfully, however, it will be understood that slight variations and changes may be made in the construction without departing from the spirit of the invention. The lens 22 may be any converging lens. convex, or it may be plane-convex-cylindrical or double-convex-cylindrical, or it may be toric. In the case of the convex cylindrical lenses, it is preferred to situate them with the axis of the convex cylinder perpendicular to the axes of the concave cylindrical surfaces of element 4. In the case of the plano-convex lens, it is preferred to situate it with the plano side facing the light source, and in the rear end of the casing 25, so that it may serve as a dust cover. The element 4 will always have the form as shown, with the concave surfaces on opposite sides respectively, their axes mutually parallel and the axes optically and geometrically centered. The radii of curvature may be equal or unequal and may be between the extreme limits or radius of an It may be double convex, plane-- inch to radius of inch. The diameter of the element 4 itself may be varied and naturally depends upon the inside diameter of the casing or mounting means. The remaining surfaces of element 4 which are not included in the concave cylindrical surfaces 5 and 6 may be cut away or omitted as hereinbefore described and as shown in Figure 7, or these portions of the element may be of any shape or design.

With these surfaces formed by grinding a cylindrical opening 4| thru the element 1, as shown in Figure 8, the element may also be circular, square, or of any other shape or design and the surfaces 42 and 43 which are on the optical axis or in axial alignment with the axes of the concave surfaces may be plane, convex, spherical, cylindrical, toric, or of any shape. These surfaces may be used in combination with a curved surface at one end and a plane or convex surface at the other, or with a plane or curved surface at one end and a beveled surface at the other. The element shown in Figure 9 which is indicated by the numeral 44 is formed with a plane surface 45 at one end which cooperates with the beveled sur-.

face 8 at the other, and the optical axis extends thru the opening 46 therein. This combination of curved, plane, and beveled surfaces with the double convex surfaces is shown in various arrangemen'ts in Figures l0, l1, and 12.

Other changes in the mounting or construction may be made as the length of the casing is variable and is preferably made from 1% inch-es to 3 inches in length. Changes may also be made in the achromatic objective lens system as the sizes of the lenses and the distance between them and also the distance between the lenses and trimmer diaphragm may vary.

The construction and general arrangement of the apparatus will be readily understood from the foregoing description. The successful per.-% formance of this system depends upon the two concave surfaces 5 and 6 in the opposite sides of the element 4, however, the same result is obtained with the concave surfaces transposed or positioned on the inside instead of the outside of the glass body. With these surfaces inside the glass body a hole is formed thru the body and with this arrangement the outside optical surfaces may be ground to an angle for the purpose of deflecting the rays by reflection as in a prism, or may have ground thereupon lens surfaces.

In normal use the apparatus may be arranged as shown in Figure 1 with the optical axis extending in a straight line from a source of light" to a photo-electric cell and with the lens system of this invention positioned between the source of light and a film which may be located between the lens system and photo-electric cell. The lamp I may be known as the exciter lamp and may be an ordinary coiled filament incandescent lamp, or a lamp of any description or any suitable source of light may be used. The rays of light will pass from this lamp in all directions and those extending in the direction of the optical axis will pass thru the lens 22 and some of these will pass into the opening in the side of the element 4 formed by the concave surface 5. Some of these rays will be diverged and as these strike the second concave surface on the opposite side of the element, they will be further diverged so that only the refined or bright rays extending substantiallly parallel to the optical axis will pass from the element 4 thru the light gate I1.

The objectionable rays are, therefore,

diverged so that they are out of the path of the light beam, whereas a large proportion of the light rays ordinarily killed by the mat or light gate are reflected into a concentrated light beam which passes through the gate. It will be appreciated that the object of any lens system is to concentrate as many light rays as possible in the light beam where they may be used instead of matting out these rays or killing them with a dark surface having a very narrow slit therein, and the double concave surfaces bring these rays down to a relatively thin concentrated light beam so that a greater number of light rays pass through the light gate. These rays will then pass thru the trimmer aperture 35 in the diaphragm 29 in which the outline of the light beam will be defined and this beam will then pass thru the achromatic lens system and from there to the film and thru the film to the photo-electric cell. Substantially the same result will be obtained in the system shown in Figure 10 except that the opposite surface of the lens 22 is positioned on the opposite side of the element which is indicated by the numeral 41 in which the concave surfaces are formed, however, the light beam will pass thru this element to the trimmer aperture in the diaphragm and from this thru the achromatic lens system to the sound track on the film and to the photo-electric cell. In the system shown in Figure 11, the optical axis will pass into the concave surfaces in the opening 46 and to a beveled surface 49 from which it will be reflected at a right angle thru the trimmer diaphragm 29 and the achromatic lenses and film to the photo-electric cell. In the diagram shown in Figure 12 the element 50 is positioned vertically so that the optical axis will pass downward thru the opening 46 until it engages a beveled surface which will deflect it thru the trimmer diaphragm, objective lenses and film to the cell 2. It will be understood that these elements and lenses may be arranged in many different positions and the concave surfaces 5 and 6 may be located at many different points and also that these surfaces may be used in combination with lenses of any other type or description. The invention is in the fact that the concave surfaces are positioned in or upon a glass body in such a manner the film. Many different arrangements may be used for recording, however, in Figure 16, one arrangement is illustrated in which a telephone or microphone 52 may be connected to an am.- plifier 53 and these may be connected to a light 54 whose luminosity is controlled by variations of amplified signals from the microphone, or any lamp whose intensity may be controlled by variable sound impulses. This lamp is positioned on the optical axis of the lens system so that the light therefrom will pass directly thru the element, which is indicated by the numeral 55, and from there thru the light gate H, the trimmer diaphragm 29 and the lenses 28 and 3| of the achromatic lens system to the film 39. This system is only typical and it will be understood that any system desired may be used.

Having thus fully described the invention what we claim as new and desire to secure by Letters Patent, is:

Apparatus for recording sound upon photographic film and reproducing it therefrom, comprising a source of light, a relatively small cylindrical casing having a lens member positioned on the optical axis of said light source having opposed concave cylindrical surfaces, a light gate through which a light beam from the concave surfaces of said lens member may pass, said lens member and light gate positioned adjacent the end of the casing positioned adjacent said light source, trimming means positioned to define said light beam adjacent the opposite end of said casing, an objective lens system positioned beyond said trimming means, and. a photo-electric cell beyond the end'of said casing, said casing and photo-electric cell positioned to permit the film to pass therebetween.

PAUL SAFRANSKI. KING ROSS. 

